1. Field of the Invention
The present invention relates to a probe apparatus for checking the electric property of an object such as a semiconductor wafer chip.
2. Description of the Related Art
In the conventional probe apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. Sho 64-73632, a probe card is positioned in an apparatus body through a card holder and a test head is arranged above it.
The probe card mainly used is of the probe-tilted type in which each probe as tilted relative to a printed plate. The other probe card different from the probe-tilted one as of the vertical probe type in which a plurality of probes extend vertical from the probe card at high density. This vertical type probe card (VTPC) has been made to meet the number of electrode pads increased and their pitch made finer as semiconductor chips are more and more integrated.
In the conventional probe apparatus, the wafer-mounted table (or wafer stage), a head plate and an insert ring are arranged parallel to one another. However, the tip level of probes becomes uneven because of attaching errors of the head plate, the insert ring and a card holder or because of making errors and deformation of the probe card itself. As the result, level of probe tip portions are differ, and the probe tip profile is tilted or shifted from its predetermined position relative to a horizontal plane.
"The probe tip profile" corresponds to a plane or a curved surface formed by an envelope extending along tips of probes.
In the case of a probe card on which the probe tip profile of each probe group is tilted or shifted. One tips of probe line or group are put in a high level position while the other tips of probe line or group are in a low position. When this tilting of probe tips of one group from those of the other group exceeds an allowable value (smaller than 20-30 .mu.m), some of the probes do not contact or incompletely contact with the pads to thereby cause full electric continuity not to be attained even if the wafer on the wafer-mounted table is over-driven or lifted over their contact point.
In recent years, the number of probes is increased in the probe apparatus now used. It is therefore quite important that the accuracy of probe tips of the probe card is high. The tilting or shifting of the probe tip profile becomes more and more of a serious problem accordingly. In the conventional probe apparatus, a microscope is set to the apparatus body, the wafer-mounted table (or wafer chuck) is lifted until the wafer is contacted with contact pins, and probe tips of each probe group contact with the wafer or their tracks on the wafer are checked through the microscope. When the probe tip profile of each probe group is tilted or shifted from their predetermined position, the probe card is re-set in the apparatus body or fasteners for the head plate are unfastened and a spacer is inserted between the head plate and its reference plane.
However, it is quite difficult to check the tilting of the probe tip level through the microscope. In addition, it is also quite difficult to find the location to insert the spacer under the head plate. Further, the probe card is not manufactured to meet the condition under which it encounters in the probe apparatus. Every probe card, therefore, can become deformed. When a heavy test head is arranged above the probe card practically set, another tilting of the probe tip profile is caused and it is quite troublesome to correct it.